Set in turn-of-the-century Japan, the film tells the story of Ginko, a Mushi Master who studies strange, iridescent creatures called "Mushi" that can't be seen by ordinary men. Having lost his memory in a childhood incident, he wanders the countryside protecting humans from the illnesses Mushi inflict. He's summoned to the bedside of a dear friend, who became infected by a Mushi after being told a story. It was the story of a powerful Mushi called "Tokoyami", which lived at th bottom of a pond, and an eyeless fish which lived at the bottom of the Tokoyami called "Ginko".